What is Pressure regulator and its operations

A pressure regulator is a valve that controls the pressure of a fluid or gas to a desired value using negative feedback from the controlled pressure. Regulators are used with gases and liquids and can be a three-in-one unit with a pressure setting,restrictor,and sensor,or they can consist of a separate pressure sensor,controller,and flow valve.There are two types: pressure reducing regulators and back pressure regulators.A pressure reducing regulator is a control valve that reduces the input pressure of a fluid or gas to a desired value at the output. It is a normally open valve installed upstream of pressure sensitive equipment.A back pressure regulator,back pressure valve, pressure maintenance valve or pressure maintenance regulator is a control valve that maintains the set pressure on its inlet side by opening to allow flow when the inlet pressure exceeds the set point.It differs from an overpressure relief valve in that an overpressure valve only opens when the contained pressure is too high and does not need to keep the upstream pressure constant.They differ from pressure reducing regulators in that pressure reducing regulators control downstream pressure and are not sensitive to upstream pressure.It is a normally closed valve that can be installed in parallel with or after sensitive equipment to impede flow and thus maintain upstream pressure.Both types of regulators use feedback of the regulating pressure as the input to the control mechanism,usually actuated by a spring-loaded diaphragm or piston,which responds to changes in the feedback pressure to control valve opening.In both cases,the valve is It should be opened just enough to maintain the set regulated pressure. The actual mechanism is probably very similar in all respects,except for the placement of the feedback pressure tap.As with other feedback control mechanisms,the level of damping is important to achieve a balance between fast response to measured pressure changes and output stability.Insufficient damping can cause oscillatory oscillations in control pressure,while excessive friction in moving parts can cause hysteresis.

Pressure reducing regulator 

Operation

The primary function of a pressure reducing regulator is to match the flow of gas through the regulator to the demand for gas while maintaining a sufficiently constant output pressure.If the load flow is reduced, the regulator flow must also be reduced. If the load flow increases,the regulator flow must increase to prevent the controlled pressure from dropping due to a gas shortage in the pressure system.For a wide range of flows,it is desirable that the control pressure vary little from the set point,but it is also desirable that the flow through the regulator be stable and the regulated pressure not oscillate excessively.A pressure regulator consists of a restricting element,a loading element and a measuring element.Throttling elements are valves that can provide variable throttling of flow,such as globe valves,butterfly valves, poppet valves, etc.A loading element is a part that can apply the required force to a restraining element.This load can be provided by a weight,a spring,a piston actuator or a diaphragm actuator combined with a spring.A measuring element is used to determine when the inlet flow equals the outlet flow.The diaphragm itself is often used as the measuring element;it can be used as a combined element.

In the single stage regulator shown in the figure, a force balance is used across the diaphragm to control the poppet valve to regulate pressure. In the absence of inlet pressure,a spring above the diaphragm pushes it down onto the poppet,keeping it open.Once inlet pressure is introduced,the open poppet valve allows flow to the diaphragm,and pressure in the upper chamber increases until the diaphragm is pushed up by the spring,causing the poppet valve to reduce flow,eventually stopping further increases in pressure.By adjusting the top screw, the downward pressure on the diaphragm can be increased, requiring more pressure in the upper chamber to maintain balance. In this way,the outlet pressure of the regulator is controlled.

Single stage regulator

High-pressure gas from the gas source enters the regulator through the air inlet.The inlet pressure gauge will indicate this pressure.The gas then passes through the normally open pressure control valve orifice,and downstream pressure rises until the valve actuating diaphragm deflects enough to close the valve,preventing more gas from entering the low pressure side,until the pressure drops again.The outlet pressure gauge will indicate this pressure.Outlet pressure on the diaphragm and inlet pressure and poppet spring force on the upstream portion of the valve hold the diaphragm/poppet assembly in the closed position against the force of the diaphragm loading spring.If the supply pressure drops,the downstream pressure will rise slightly to compensate due to the reduced closing force caused by the supply pressure.Therefore,if the supply pressure drops, the outlet pressure will increase,provided the outlet pressure remains below the falling supply pressure.This is the reason for tank tail dumps supplied by pressurized gas tanks.The operator can compensate for this effect by turning the knob to adjust the spring load to restore the outlet pressure to the desired level.For single-stage regulators,when the supply pressure goes lower,the lower inlet pressure causes the outlet Pressure rises.If the diaphragm-loaded spring compression is not adjusted to compensate,the poppet can remain open and allow the tank to quickly dump its remaining contents.

Dual stage regulator

Two-stage regulators are two regulators in series in the same housing that gradually reduce pressure in two steps instead of one.Preset the first stage,reduce the gas supply pressure to the middle stage;the gas under this pressure enters the second stage.Gas is exhausted from the second stage at a user-set pressure (operating pressure) by the user by adjusting the pressure control knob on the diaphragm-loaded spring.Two-stage regulators may have two safety valves so that if there is excessive interstage pressure due to a seat leak in the first stage,the rising pressure does not overload the structure and cause an explosion.Unbalanced single-stage regulators may require frequent trimming.As supply pressure drops, outlet pressure may change requiring adjustment.In two-stage regulators,improved compensation for supply pressure drops.